This study will evaluate function of the intact dog left ventricle with hypertrophy due to pressure overload and volume overload. Pressure overload will be induced by banding of the ascending aorta. Volume overload will be induced by chronic, severe exercise. Evaluation of left ventricular performance will be done using biplane cine radiography in the intact animal. Quantitation of left ventricular angiograms will be done by computer to provide a multiparametric analysis of function. In conjunction with mechanical data, myocardial myosin ATPase activity will be quantitated and correlated with changes in mechanical function. Similar evaluation will be undertaken after removal of the hypertrophy stimulus. These studies will improve understanding of the mechanical alterations of the heart hypertrophy, the differences between volume and pressure overload hypertrophy, the reversibility of myocardial lesions in hypertrophy and the cardiac response to exercise.